This invention relates to novel apparatus for filtering liquids in a closed system wherein liquid is transferred between containers affixed to a housing with fluid transfer occurring through channels in the housing. The driving force for the fluid transfer is provided by a pressurized stream of inert gas.
In semiconductor manufacturing operations, product yield is determined in part by the cleanliness of the manufacturing environment and the purity of the raw materials used in the manufacturing operations. The environment is controlled by the manufacturer. The purity of the products is dependent on the care taken by the product provider in treating the products. The increasing expansion of capacity and the competitiveness in pricing now existing in the semiconductor manufacturing industry has created a great need for maintaining yields at a high level. To accomplish this goal, a need exists for efficiently providing solutions of all types which reliably conform to the specifications of the process being used. Among the types of treated solutions used are aqueous solutions, alcohols, ethyl acetate, acids and caustic liquids. The presence of particulate matter in these solutions directly impacts the manufacturing yield especially in connection with the manufacture of the semiconductor wafers. Any impurities left on the surface of semiconductor wafers at the start of processing generally manifest themselves as unacceptable integrated circuits which do not survive product testing. Since the effects of the impurities are not usually determinable until the manufacturing processes have been completed, the manufacturing yield drops for finished products.
In systems used for the removal of particulate matter from solutions, it is important to utilize inert material in the filtration system and containers. At present, stainless steel equipment is used in combination with polyetrafluraethylene (Teflon) coatings. These laminated and coated parts are expensive to manufacture and do not fully solve the problem since Teflon has a tendency to delaminate during use. One result of the delamination of system components is that iron, boron and nickel are leached from the stainless steel and serve as contaminants of the processed solutions. Frequently, the filtration systems used to separate out particulate matter from treatment solutions are located in a clean room due to the filtration system not being a closed system. The costs associated with the utilization of a clean room are substantial and contribute to the costs of the products being processed.
Accordingly, the present invention is directed to a closed system for the filtration of particulate matter from liquids which utilizes low cost, inert materials in a unitary structure which conducts filtration without exposure to the surrounding environment. The filtration system provides ready access to containers for the liquid being treated as well as to a disposable filter in fluid communication with the containers. In addition, the present provides a light weight, compact and easily transportable housing which is affixed to containing fluid transfer channels therein and adjacent liquid containers. The housing is coupled to a pressurized source of inert gas which provides the driving force for the liquid transferred between adjacent containers. A disposable filter included in the fluid flow path is affixed to the housing to complete the unitary structure.